Chiral tilted smectic liquid-crystalline phases having ferroelectric properties can be prepared by adding one or more tilted smectic phases containing a suitable chiral additive to basic mixtures (L. A. Beresnev et al., Mol. Cryst. Liq. Cryst. 89, 327 (1982); H. R. Brand et al., J. Physique 44 (lett.), L 771 (1983). Such phases can be used as dielectrics for fast switching displays which are based on the principle of SSFLC technology, described by Clark and Lagerwall (N. A. Clark and S. T. Lagerwall, Appl. Phys. Lett. 36, 899 (1980); U.S. Pat. No. 4,367,924), based on the ferroelectric properties of the chiral tilted phase. In this phase, the elongated molecules are arranged in layers, the molecules having an angle of tilt with respect to the layer normal. On progressing from layer to layer, the direction of tilt changes by a small angle with reference to an axis perpendicular to the layers, with the result that a helical structure is formed. In displays based on the principle of SSFLC technology, the smectic layers are arranged perpendicularly to the plates of the cell. The helix-like arrangement of the directions of tilt of the molecules is suppressed by a very small spacing of the plates (approximately 1-2 .mu.m). This forces the long axes of the molecules to arrange themselves in a plane parallel to the plates of the cell, as a result of which two distinct tilt orientations are produced By applying a suitable electrical alternating field it is possible to switch back and forth between these two states in the liquid-crystalline phase, which has a spontaneous polarization. This switching operation is substantially faster than in conventional twisted cells (TN LCDs) based on nematic liquid crystals.
A great disadvantage for many applications of the currently available materials having chiral tilted smectic phases (such as, for example, S.sub.C *, but also S.sub.h *, S.sub.I *, S.sub.J *, S.sub.K *, S.sub.G *, S.sub.F *) is their low chemical and thermal stability and low photostability. A further disadvantageous property of displays based on currently available chiral tilted smectic mixtures is that the spontaneous polarization has unduly low values, with the result that the switching time behavior of the displays is unfavorably affected and/or the pitch and/or the tilt and/or the viscosity of the phases does not meet the requirements of display technology. In addition, the temperature range of the ferroelectric phases is unduly small and is predominantly at unduly high temperatures.